1. Field of the Invention
This invention relates to a process for producing organic compounds by utilizing oxygen complexes as oxidizing agents, and more particularly it relates to a process for producing oxygen-containing organic compounds by the use of oxygen complexes.
2. Description of the Prior Art
Acetic acid and aldehydes as basic chemicals for petrochemical industry have been produced by oxidation reactions of suitable organic substrates as raw materials. Such oxidation reactions occupy an important situation among reaction processes having been employed in the petrochemical industry. These oxidation reactions, however, have so far been carried out under high temperatures and high pressures, and by-products are generally formed at the same time; the improvement of the selectivity and yield of such reactions has become an important problem. For example, in the preparation of carboxylic acids from aldehydes, an oxygen-oxidation process using transition metal ions such as ions of Co, Mn, etc. as catalyst has been practically employed. The reaction mechanisms of the process considered to be that a metal ion is first oxidized with oxygen into a high valence state ion such as Co(3) or Mn(3), followed by oxidizing aldehydes by means of the Co(3) or Mn(3). However, it has been said that the processes are complicated reactions accompanied with radical formation and since the reaction temperature must be controlled in the vicinity of 50.degree. to 70.degree. C. because the oxidation reaction further advances to produce such by-products as formic acid and CO.sub.2. Thus, high yield cannot be expected, and complicated separation steps are required for purification of the resulting product.
On the other hand, as to the oxygen complexes functioning as an effective oxidizing agent for oxidation reactions of organic sustances, various studies have been made as model reactions of the respiratory reaction of living bodies. For example, there are iron-protein and copper-protein compounds in mammals and molluscs, respectively. These are complex compounds consisting of the protein and divalent iron or monovalent copper ion.
Usually, in the case of metal ions capable of taking various valences, the low valence ions thereof are contacted with oxygen to form high valence metal ions through oxidation, as expressed by the following equations: EQU Cu(1)+1/4O.sub.2 +1/2H.sub.2 O--Cu(2)+OH.sup.- ( 1) EQU Fe(2)+1/4O.sub.2 +1/2H.sub.2 O--Fe(3)+OH.sup.- ( 2)
However, in the case of hemoglobin or hemocyanin wherein Fe(2) cr Cu(1) is reacted with a protein in advance to form a protein complex, it has been known that even if such a complex is contacted with oxygen, there occurs no direct oxidation reaction of metal ions, but oxygen in the form of molecule is coordinated with metal ions in the complex (i.e. formation of an oxygen complex), as follows ("chemistry of metal proteins" in Japanese, edited by Ohtsuka and Yamanaka, Kohdansha (1983)): EQU P--Fe(2)--O.sub.2 --Fe(2)--P, EQU P--Cu(1)--O.sub.2 --Cu(1)--P (3)
wherein P represents a protein.
The oxygen molecule thus combined is activated by its coordination with metal ions, to have a performance of oxidizing of various organic substances at low temperatures such as the body temperature of living bodies, and its reaction heat constitutes the energy source of living bodies. However, if such a protein complex is separated from living bodies, it becomes unstable, and the metal ion is readily oxygen-oxidized to higher valence state. Thus, with respect to its application to industrial oxidation reactions, it is a big problem to employ an artificial compound as a complexing agent and to combine this compound with a suitable transition metal to thereby producing a complex capable of forming a stable oxygen complex.
The object of the present invention is to solve the above problem and provide a process for oxidizing organic compounds by which aimed oxygen-containing organic compounds can be produced with a high selectivity and a good yield.